Sonography is becoming the technique of choice as a diagnostic aid in many surgical procedures since it does not involve any radiation danger to the patient, and it has become especially useful in obstetrical imaging and in treatment of human infertility by in-vitro fertilization and embryo transfer (IVF/ET). Diagnostic ultrasound has proved to be valuable for oocyte pickup in IVF/ET programs since ultrasound can guide a needle to a small target within the human body.
The original procedures using ultrasound in IVF/ET included abdominal imaging and puncturing; however, trans-abdominal scans limited image resolution because of the large distance from the target area to the probe. More recently, transvaginal imaging using a vaginal transducer and a transvaginal puncturing technique has been developed. This technique has been described in the paper by Wikland et al "Use of a Vaginal Transducer for Oocyte Retrieval in an IVF/ET Program", J. Clin. Ultrasound 15:245-251, May 1987, and in U.S. Pat. No. 4,742,829 to Law et al issued May 10, 1988, for "Intracavitary Ultrasound and Biopsy Probe for Transvaginal Imaging".
To improve the accuracy of puncturing in the target area, various devices have been designed to guide the needle into the selected body site. However, in general, these devices require that the needle assembly be mounted on the probe before insertion of the probe into the vagina. It is desirable to provide a needle guide holder for an ultrasound imaging system in which the needle guide can be placed on or removed from the probe while the transducer is still in the vagina so that the instruments can be placed in the urethra and vagina at separate times.